Several types of dipsticks are known to the art. All of these dipsticks provide a manual means for monitoring fluid levels in engines. However, the means by which the dipstick cap is secured to the fill tube, and the design of the dipstick blade, vary considerably. For example, U.S. Pat. No. 3,703,038 (Smith) discloses an oil dipstick with a wiper housing. The rod rotates within the wiper housing so that the fluid residue will not be accidentally wiped from the fluid level indicia on the rod when the rod is removed from the fill tube. U.S. Pat. No. 5,022,495 (Lavender) discloses a dipstick with an s-shaped blade. The cap of the dipstick is equipped with flanges so that it locks into place when it is turned. U.S. Pat. No. 5,086,943 (Poskie) discloses a dipstick useful for monitoring the level of transmission fluid. The dipstick has a screw-on cap which is fitted with an o-ring to perfect the seal of the cap. The blade of the dipstick is molded to the cap and has a series of horizontal and vertical indicia.
In many engines, the seal integrity between the dipstick cap and the fill tube is important to prevent fluid leakage. In these applications, screw-on caps are usually employed to effect a tight seal. However, many of the more complex modern engines are crowded in the vicinity of the fluid reservoir, and therefore require nonlinear fill tubes. To date, it has not been possible to use conventional dipstick designs and screw-on caps with nonlinear fill tubes, since the blade of the dipstick, when bent, is pressed against the side of the fill tube as the cap is turned, thereby arresting its movement. This problem was recognized, for example, in U.S. Pat. No. 5,022,495 (Lavender), Col. 1, Lines 20-23.
It is thus an object of the present invention to provide an inexpensive, easy to use, improved dipstick with a screw-on cap that is capable of being used with nonlinear fill tubes.